Dental cements
Cement (from Lat. caementum — chips of stone) is a dental material consisting of powder and liquid. The powder is a crushed product of sintering of limestone, clay and slags at high temperature (clinker). Depending on the type of cement, the liquid is an aqueous solution of acids or oils. When the components are mixed, the material is cured with a transition from the viscous to solid state.
Cements came into dental practice from construction; from the beginning, they were used for the fixation of orthopedic structures, rather than for fillings or restorations.
Key principles in working with cements
Mixing time is the duration recommended by the manufacturer for blending cement components and preparing the cement mass.
Working time is the period for introducing and shaping the material while it maintains its plasticity.
Setting time is the duration in which the material undergoes initial curing.
Final maturation time of cements indicates the period when all chemical reactions are entirely completed, and the material attains its ultimate strength.
Requirements for cements
- Chemical resistance, minimal solubility (should not dissolve in water and liquids in the mouth).
- Mechanical strength (resistance to abrasion under chewing load).
- Meeting aesthetic requirements (color, transparency).
- Good adhesionChemical or mechanical adhesion between heterogeneous surfaces (between filling materials and dental tissues, between different filling materials). to the dental tissues.
- Thermal expansion coefficient that is close to the thermal expansion coefficient of the tooth tissues.
- Low thermal conductivity (to exclude thermal irritation of the pulp).
- Absence of shrinkage.
- Biocompatibility (safety for pulp, mucosa, etc.).
- Setting in the presence of water and saliva.
- Radiopacity.
- Sufficient mechanical strength.
- Good handling properties (plasticity, ease of insertion into the caries cavity, duration of «working time», etc.).
- Cements can be classified according to several criteria:
- intended use (clinical classification);
- composition [D.S. Smith classification (1995–1998)];
- by formation reaction: cements mixed in water (hydraulic cements), cements formed as a result of acid-base reactions (phosphate and polycarboxylate).
By their intended purpose, cements can be divided into temporary or permanent cements (Table 2.1, Fig. 2.1).
Table 2.1. Classification of cements by purpose
| Permanent | Temporary |
| For cementation of dental prostheses | For cementation of dental prostheses |
| For restorations | For restorations |
| For direct and indirect pulp coating | For direct and indirect pulp coating |
| Base and isolating liners | Base and isolating liners |
| For root canal filling | For root canal filling |
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Fig. 2.1. Filling structure: 1 — treatment (curative) liner, 2 — isolating liner, 3 — base liner, 4 — main restorative material
D.S. Smith classification of cements according to composition (1995–1998).
- Phenolate (based on water and phenolates):
- zinc-eugenol:
- polymer-reinforced;
- EBA modified (o-ethoxybenzoic acid);
- aluminous;
- calcium-hydroxide-salicylate.
- Mineral (based on aqueous solutions of phosphoric acid):
- zinc-phosphate;
- silicate;
- silicophosphate.
- Polycarboxylate (based on aqueous solutions of organic acids):
- zinc-polycarboxylate;
- glass ionomer (polyalkenoate).
- Acrylate (based on acrylates):
- poly(methyl acrylate);
- dimethylacrylate:
- with filler;
- without filler.
Currently, due to the development of materials science for cements and the emergence of new groups of materials, this classification may not accurately reflect the composition. In particular, this applies to aluminous cements, which are currently considered as a separate group of hydraulic materials.
Phenolate cements
Phenolate cements include:
- zinc-eugenolic materials:
- polymer-reinforced;
- EBA modified (o-ethoxybenzoic acid);
- aluminous: zinc-sulfate, Portland cement-based materials [materials containing mineral trioxide aggregate (MTA), bioceramic];
- calcium-hydroxide-salicylate materials.
Composition zinc-eugenol cements is presented in Table 2.2.
Table 2.2. Composition of zinc-eugenol cements
| Types of cements | Liquid | Powder | Reaction product |
| Non-modified zinc-oxide-eugenol cement | Eugenol | ZnO | Crystalline zinc eugenolate |
| Zinc-oxide-eugenol polymer-reinforced cement | Eugenol | ZnO, polymer resin | Crystalline zinc eugenolate |
| Modified EBA (o-ethoxybenzoic acid) | Eugenol, o-ethoxybenzoic acid | ZnO, Al2O3, polymer | Crystalline zinc eugenolate, crystalline ethoxybenzoate |
| Dentin paste/oil dentin | Peach oil (apricot), eugenol | ZnO, kaolin, zinc sulfate | Crystalline zinc eugenolate |